Many industrial processes require a reliable source of high purity process gases for a wide variety of applications. Often these gases are stored as liquids or as a liquid-vapor mix under pressure in containers and then delivered to the process point of use under controlled conditions from the containers.
To satisfy the high purity requirements for gaseous products imposed by these industries, particularly the semiconductor industry, various fill operations have been employed. For example, containers employed for storage and delivery are specifically prepared for cleanliness, and elaborate measures are taken during manufacture and product fill to maintain purity standards. Despite these measures the product purity of the respective gases tends to degrade during storage and the resulting degradation products must be removed prior to delivery of the gaseous product for on-site use. Contamination of the gaseous product also may occur during vapor withdrawal through entrainment of particulates. These contaminants also must be removed prior to on-site use.
On-site purifiers and containers with built-in purifiers have been employed for removal of contaminants, e.g., the removal of degradation products and particulates, in order to assure delivery of high purity gaseous product to the point of application. Purifiers employing carbon based and other adsorbents have limited effectiveness for removal of all contaminants and adsorption processes also require periodic adsorbent replacement to avoid sudden breakthrough contamination.
The following articles and patents are representative of the art:
U.S. Pat. No. 5,409,526 discloses an apparatus for supplying high purity fluid from a cylinder by means of withdrawing the fluid from the cylinder through a purification unit containing adsorbents. The purification unit is internal to the cylinder.
U.S. Pat. No. 5,461,870 discloses a self-refrigerated process for cryogenic refrigeration employing a heat exchanger whereby a gas comprised of at least two condensable components having different condensation temperatures is treated in a unitary assembly. The apparatus includes heat exchangers of the purifier type.
U.S. Pat. No. 6,442,969 discloses a process for the separation of gases, e.g., carbon dioxide from methane using reflux exchangers.
U.S. Pat. No. 6,349,566 discloses a purifier system installed within a pressure vessel for the purpose of eliminating headers, collectors and the like.
U.S. Pat. No. 5,983,665 discloses a process for producing liquid methane employing a purifier. A feed gas is cooled in a heat exchanger, partially condensed and then rectified in the purifier.
U.S. Pat. No. 5,802,871 discloses a process for removing nitrogen from a methane gas by cooling, partially condensing and then rectifying the methane in at least one purifier.
U.S. Pat. No. 5,694,790 discloses a process for the rectification of an air stream in a heat exchanger having a first set of passages for separating the components by dephlegmation.
U.S. Pat. No. 5,144,809 discloses a process for the production of nitrogen by cooling a feed gas air stream in an apparatus employing a parallelepipedal heat exchanger.
U.S. Pat. No. 5,017,204 discloses a process for producing helium from a natural gas stream by rectification of the feed gas in a purifier heat exchanger. The system is auto-refrigerated and does not require a heat pump or recycle compressor.
U.S. Pat. No. 4,110,996 discloses a method and apparatus for recovering vapor from a container during the filling thereof. Vapor is collected cooled and condensed. The condensate is separated from the vapor and is used to further cool and condense vapor.